494 P^fof. Piazzi SmylKs Account of the [March 5, 



serene and quiet air, such as may perhaps be found on the tops of 

 the highest mountains, above the grosser clouds." 



This appears a very simple and probable piece of speculation, 

 yet somehow it dropped out of notice, and never had the seal of 

 practical trial applied to its theoretical prediction, until the late 

 First Lord of the Admiralty, Sir Charles Wood, duly advised by 

 the Astronomer-Royal, Mr. Airy, commissioned me to make the 

 attempt in the summer of 1856, by carrying a large telescope to a 

 considerable height up the flanks of the Peak of Tenerifle. 



That mountain was chosen as the most elevated one within 

 reach of a summer expedition, and at the same time of practicable 

 ascent with large instruments. It is situated, moreover, in the 

 middle of the N.E. trade wind region, where the weather is not 

 only more regular than in any other part of the world, but where, 

 mutatis mutandis, some pretty certain data as to the climate of the 

 upper atmospheric strata, had been procured from another and 

 grander scientific work, recently performed, also under the Lords 

 of the Admiralty, viz., the remeasurement of La Caille's Arc of 

 the Meridian at th^ Cape of Good Hope, by their Lordships' 

 southern astronomer, Mr. Maclear. 



Further particulars of a practical nature, relative to the cha- 

 racter of the ground, as well as the temper and quality of the inha- 

 bitants, having been procured from Robert Stephenson, M.P., who 

 had lately visited the island, and whose early experiences on South 

 American cordilleras, had long since led him to look with favour 

 on Newton's mountain method of improving astronomical observa- 

 tion, — the preparations for this novel sort of expedition went on 

 quickly during May and June. 



At this stage, so much kindly interest in the attempt was shown 

 in the limited circle of working astronomers, that, beginning with 

 Mr. Airy, I was favoured by them in the course of a few weeks 

 with the loan of many valuable instruments ; and finally, Mr. 

 Stephenson, who had already paved the way to the expedition being 

 called into being, tendered the magnificent contribution of no less 

 than the use of his yacht Titania, and her able crew. With them, 

 accordingly, we set sail on June 22nd from Cowes ; I say we, for 

 I was accompanied by my wife, the best assistant that either an 

 astronomer or any other man can possibly have. 



There was still just a trifle of uncertainty spread over our 

 prospects, for some very opposite opinions were in the field, appa- 

 rently supported by observed facts ; and a few voices even loudly 

 proclaimed, that high mountain tops, all the world over, are inva- 

 riably loaded with clouds and mist and sleet, and tormented for 

 ever with impetuous storms. Yet strong in our own belief, on we 

 went in the swift Titania, and arriving in Tenerifle on July the 8th, 

 were at once made free of the island by the liberal and hospitable 

 Spanish authorities ; beginning our first ascent six days afterwards, 

 with a long line of mules laden with instruments and baggage. 



